Compensating for Parasitic Effects in Low-Pass Filters

Techniques to compensate for the effects of parasitic inductances and capacitances have been developed as part of an effort to improve the performances of low-pass filters in electronic power circuits. As used here, "parasitic" refers to departure from an ideal inductive or capacitive characteristic. No inductor, capacitor, or other electronic component is ideal: wherever a current loop exists, there is inductance, and wherever two conductors are near each other, there is a capacitance between them. Parasitic capacitances in inductors and parasitic inductances in capacitors degrade the performances of low-pass filters, especially at high frequencies.

Posted in: Briefs, Electronics & Computers, Capacitors, Power electronics, Performance upgrades

Fast Liquid-Crystal-on-Silicon Spatial Light Modulators

Stressed-liquid-crystal (SLC) light-modulating devices suitable for use as liquidcrystal- on-silicon (LCOS) spatial light modulators (SLMs) that could operate in nearand mid-infrared wavelength ranges have been demonstrated. These SLC devices were conceived to exploit the SLC electrooptical effect, which makes it possible to obtain response times shorter than those of prior infrared LCOS SLMs.

Posted in: Briefs, Photonics, Optics, Semiconductors, Silicon alloys

Detecting Change in 3D by Use of an Evidence Grid

Astudy has been undertaken to evaluate a method of detecting change in a three-dimensional (3D) terrain map generated from data acquired by an imaging ladar system carried aboard a moving unmanned ground vehicle (UGV) on patrol. The proposed method involves the use of an evidence grid (described below) in comparing data acquired on a second patrol with data acquired on the first patrol along the same route, in order to determine which, if any, volume elements (voxels) in a 3D map representing the terrain have changed from free space to occupied or vice versa. For the purpose of the method, it is assumed that the terrain is static during each patrol and the only changes of interest occur between patrols. It was recognized in the study that these assumptions are unlikely to hold in realistic scenarios. This study was intended to be a precursor to a study of a method for recognizing a moving obstacle C, particularly a moving pedestrian C during a patrol by an autonomous UGV.

Posted in: Briefs, Photonics, Cartography, Lidar, Surveillance, Terrain, Autonomous vehicles, Military vehicles and equipment

Accelerated Evaluation of Properties of Polyphase Alloys

A methodology for accelerated evaluation of mechanical properties of polyphase alloys is based on digital representations of the alloys. For a given alloy material system, this representation is utilized in concert with (1) software tools and probes that simulate traditional laboratory testing equipment and instrumentation, and (2) real laboratory mechanical testing by nontraditional methods.

Posted in: Briefs, Materials, Computer simulation, Alloys, Materials properties, Test equipment and instrumentation, Test procedures

Plasma-Spray Coating as an Alternative to Chromium Plating

Plasma-spray application of coating materials that include tungsten carbide has been investigated as an alternative to electroplating of hard chromium onto internal metal surfaces that are required to be protected against wear or to be restored to within dimensional tolerances. Prime examples of such wear surfaces are the inner walls of cylinders in aircraft hydraulic actuators and dampers. The need for an alternative to chromium plating arises partly because chromium plating involves the use of hexavalent chromium, which is a highly toxic carcinogen subject to increasingly stringent government regulation and, therefore, increasingly expensive to use. Another reason for developing an alternative arises from a desire to reduce process time: To remove hydrogen that is unavoidably incorporated during chrome plating, it is necessary to perform a 24-hour bakeout. Process time could be reduced substantially if this bakeout could be eliminated. Plasma spraying involves fewer process steps than does electroplating, and for plasma-sprayed coatings, no hydrogen bakeout is necessary.

Posted in: Briefs, Materials, Spraying, Coatings Colorants and Finishes

Measuring Glucose Using pH-Sensitive Hydrogels

Sensors that exploit pH-sensitive hydrogels for measuring concentrations of glucose in aqueous solutions are undergoing development. Because the underlying chemical and physical principles are also applicable to sensing of biochemicals other than glucose, it is expected to be relatively easy to modify the glucose sensors to enable detection of such biochemicals.

Posted in: Briefs, Materials, Sensors and actuators, Water, Biomaterials, Chemicals

Thrust-Augmented Nozzles for Rocket Engines

The thrust-augmented nozzle (TAN) has been invented as a means of obtaining high performance from a rocket engine both during liftoff at sea-level atmospheric pressure and later during flight under near-vacuum conditions. In effect, the TAN rocket engine amounts to a booster rocket engine contained entirely within a sustainer rocket engine, and very little weight is associated with the incorporation of the TAN portion. Heretofore, it has been difficult or impossible to design the same rocket engine to perform well at both extremes of ambient pressure.

Posted in: Briefs, Mechanical Components, Performance upgrades, Nozzles, Booster rocket engines, Reliability

Thermal Design and Analysis of a Rocket-Engine TAN Injector

A subscale thrust - augmented - nozzle (TAN) rocket engine was designed, built, and hot-fire tested to demonstrate the validity of the TAN concept. As described in more detail in the immediately preceding article, in a TAN, during operation at sea level, thrust is augmented through injection and burning of secondary propellants (a fuel and an oxidizer) within the nozzle, downstream of the nozzle throat. The secondary propellants can be the same as, or different from, the primary propellants (the fuel and oxidizer burned during operation, in a near vacuum, in the absence of thrust augmentation).

Posted in: Briefs, Mechanical Components, Propellants, Nozzles, Booster rocket engines, Fuel injection

Two-Processor Autopilot System for a UAV

Atwo-processor autopilot control system for an unmanned aerial vehicle (UAV) has been proposed and partly developed. Relative to prior such systems, this would be a lightweight, inexpensive autopilot system offering enhanced computational power and flexibility that would enable the use of the system in a variety of advanced UAVs. The two-processor architecture represents a significant departure from most prior single-processor UAV-autopilot architectures. Moreover, because this particular two-processor architecture is an open one, based on the use of commercial- off-the-shelf (COTS) processors and other COTS electronic subsystems, the system could easily be upgraded to take advantage of available state-of-the-art equipment.

Posted in: Briefs, Information Technology, Architecture, Unmanned aerial vehicles

Automatic Abstraction of Information From Digitized Images

A research effort now underway addresses fundamental mathematical issues involved in a methodology of creating flexible machine vision systems that would be able to modify their behaviors and evolve in particular environments so as to recognize anything that human operators have designated as being "interesting" in those environments. It is intended that a person who is not a programmer could train such a machine vision system by drawing lines around objects in a scene (see figure) or otherwise indicating example objects and that thereafter, the system would adapt and evolve the ability to recognize such objects automatically.

Posted in: Briefs, Information Technology, Imaging